Mobile devices have been widely used for communication among people. It is common for people to use cellular phones, personal digital assistants, and other wireless devices on a mobile structure, such as a moving vehicle, train, ship or ferry. To support these applications, conventional systems provide either absolute coordinates of the mobile devices (e.g. latitude and longitude) or coordinates relative to some fixed reference point (e.g. a point associated with some fixture on the ground) whose absolute location is or can be known. Such absolute or relative coordinates are not always useful for specifying location of a mobile device relative to a mobile structure that the mobile device is on or within because the location and orientation of the mobile structure may not be known, or if known, may change. In some situations, for example if one is trying to locate the user of a mobile device on a moving cruise ship or train, the absolute position of the mobile device or the position relative to some fixed reference point may not be as useful as the relative position of the mobile device with respect to the moving cruise ship or train.
Therefore, there is a need for systems and methods that can address the above issues of the conventional systems.